The invention relates to a process for the production of colored ceramic material, for example tableware, decorations which have an increased resistance to the formation of traces of wear (scratches) caused by cutlery.
The production of colored decorations on ceramic materials, such as, for example tableware made of earthenware, bone china and porcelain, is known per se (see Ullmann's Enzyklopadie der technischen Chemie, 4th Edition. Vol. 14 (1977), pp. 9-10). By means of highly diverse application techniques, such as painting, immersion, spraying, and in particular direct or indirect imprinting, a decoration coloring substance is applied in the form of a decoration onto the material to be decorated and subsequently fired in.
Decoration coloring substances comprise substantially a coloring component, conventionally a pigment, and a glass flux conventionally containing one or more glass frits. In the case of tableware decorations, it is necessary to differentiate between on-glaze and in-glaze decoration. In general, after glaze firing, a decoration is applied onto the tableware part to be decorated, for example, by means of direct printing or indirect printing (transfer pattern technique), and subsequently fired in. In the case of an on-glaze decoration either normal firing at approximately 780 to 900.degree. C. or high-temperature quick firing at temperatures above 900.degree. C. to approximately 1100.degree. C., is used. In the case of an in-glaze decoration firing is conducted at temperatures in the range of approximately 1100 to 1250.degree. C.
Porcelain tableware, in particular hotel and restaurant porcelain, is subjected to high stress through alkaline washwater of dish washing machines and through the effect of cutlery during use. Cutlery effects on decorated tableware parts lead to gray abrasion traces, which interfere with the aesthetic impression. Such abrasion traces caused by metal cutlery are especially disturbing in large-area decorations which are increasingly in demand by the market. Until now, this problem could only be solved partially through an in-glaze decoration wherein the decoration becomes partially submerged in the glaze layer during the firing.